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Question 17 of 25

Which of the following solutions would be expected to have a pH greater than 7.00?

A. [tex]NH_4Br[/tex]

\begin{tabular}{|c|c|c|c|}
\hline
Weak Acid & [tex]$K_a$[/tex] & Weak Base & [tex]$K_b$[/tex] \\
\hline
HCN & [tex]$4.9 \times 10^{-10}$[/tex] & [tex]$HONH_2$[/tex] & [tex]$1.1 \times 10^{-8}$[/tex] \\
\hline
HNO_2 & [tex]$4.5 \times 10^{-4}$[/tex] & [tex]$NH_3$[/tex] & [tex]$1.8 \times 10^{-5}$[/tex] \\
\hline
HIO & [tex]$2.3 \times 10^{-11}$[/tex] & [tex]$C_6H_5NH_2$[/tex] & [tex]$4.3 \times 10^{-10}$[/tex] \\
\hline
HBrO & [tex]$2.5 \times 10^{-9}$[/tex] & & \\
\hline
CH_3COOH & [tex]$1.8 \times 10^{-5}$[/tex] & [tex]$C_2H_5NH_2$[/tex] & [tex]$5.6 \times 10^{-4}$[/tex] \\
\hline
HF & [tex]$6.3 \times 10^{-4}$[/tex] & & \\
\hline
\end{tabular}

B. [tex]C_6H_5NH_3Br[/tex]

C. [tex]Ca(NO_3)_2[/tex]

D. [tex]C_6H_5COONa[/tex]

Sagot :

GinnyAnsweridn
To determine which of the given solutions would have a pH greater than 7.00, we need to consider the nature of each compound (whether it forms acidic, basic, or neutral solutions when dissolved in water).

1. [tex]$NH_4Br$[/tex]:
- [tex]$NH_4^+$[/tex] (ammonium ion) is a weak acid.
- [tex]$Br^-$[/tex] (bromide ion) is a neutral ion because it comes from the strong acid HBr.
- Hence, [tex]$NH_4Br$[/tex] in water will produce a slightly acidic solution, and the pH will be less than 7.

2. [tex]$C_6H_5NH_3Br$[/tex] (aniline hydrobromide):
- [tex]$C_6H_5NH_3^+$[/tex] (anilinium ion) is a weak acid.
- [tex]$Br^-$[/tex] is neutral.
- This will also result in a slightly acidic solution, and the pH will be less than 7.

3. [tex]$Ca(NO_3)_2$[/tex] (calcium nitrate):
- Both [tex]$Ca^{2+}$[/tex] and [tex]$NO_3^-$[/tex] are neutral ions (since [tex]$NO_3^-$[/tex] comes from a strong acid [tex]$HNO_3$[/tex] and [tex]$Ca^{2+}$[/tex] does not affect pH).
- Therefore, [tex]$Ca(NO_3)_2$[/tex] results in a neutral solution with a pH around 7.

4. [tex]$C_6H_5COONa$[/tex] (sodium benzoate):
- [tex]$C_6H_5COO^-$[/tex] (benzoate ion) is the conjugate base of benzoic acid, which is a weak acid.
- [tex]$Na^+$[/tex] is a neutral ion.
- The benzoate ion will hydrolyze in water to produce [tex]$OH^-$[/tex] ions, making the solution basic.
- Hence, [tex]$C_6H_5COONa$[/tex] will have a pH greater than 7.

Based on this analysis, the compound that would be expected to have a pH greater than 7.00 is:

D. [tex]$C_6H_5COONa$[/tex].
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